“Women who are depressed before conception are more likely to have depression after birth, which can have a negative influence on parenting,” Dr Moss said.

“Their children are more likely to feel angry or worried, not get along with others, not smile or laugh, or have difficulty paying attention and keeping up at school.”

One in five Australian mothers experience depression according to the Australian Institute of Health and Welfare (2012), making it a significant public health concern.

“We analysed 20 years of longitudinal data to find the best time for intervention,” Dr Moss said.

“If you’re planning a family, it’s important to add mental health to your pre-conception check list, along with more well-known factors like stopping smoking and drinking, maintaining a healthy weight and exercising.

“If symptoms of depression decrease before pregnancy, outcomes are better for women and their children.

“If you think you might have depression, start by talking to your GP – ask for help and keep asking until you find the help that works for you.

“Australian guidelines recommend mental health screening for women before and after pregnancy, but health professionals could start these conversations with women when they start trying to conceive,” Dr Moss said.

Researchers combined survey data on children’s development from the Mothers and their Children’s Health (MatCH) study with more than 20 years of longitudinal data on mother’s mental health from the Australian Longitudinal Study on Women’s Health.